Metallurgy often involves the addition of chemical elements to the molten metal to alter its composition and properties. Some additions are made with the expectation that they will react with other elements in the melt to aid in the removal of said elements. These addition agents may be referred to as deoxidizers and desulfurizers in the case of steelmaking. Other additions are made to alloy the melt and in the case of steelmaking may include ferromanganese, ferrosilicon, ferrochromium, nickel, copper, lead, aluminum to mention but a few.
Addition agents are typically added to the molten bath near the end of the refining process, to the bath in the teeming ladle or to the mold itself.
Introduction of the addition agents to the bath in the refining vessel or teeming ladle (this application does not relate to adding addition agents to the mold) presents a number of problems. Often, the molten metal is covered by a slag layer through which the addition agent must penetrate. The agent has need to be mixed throughout the molten bath and thus requires introduction of the agent deep within the bath. For certain addition agents, for example ferroalloys added to steel, the agent must be preheated to avoid chilling the bath and/or they must be mixed with chemical reagents that cause exothermic reactions. One technique for adding addition agents comprises providing a wire (of the agent) with a coating and reeling the wire deep into the melt (See, for example, U.S. Pat. Nos. 2,577,837 and 3,729,309). Yet another technique involves the use of an immersion bell or plunger (See, for example, U.S. Pat. Nos. 2,776,206, 3,788,624 and 3,942,775). In still another technique, the addition agent is carried into the bath in a stream of inert gas either though a tube passing through the surface of the melt or through the vessel walls (See, for example, U.S. Pat. Nos. 3,575,695 and 3,980,469). One ancient patent suggests forcing addition agents reduced to a proper degree of fineness through a port in the base of the vessel or ladle (See, for example. U.S. Pat. No. 165,929).
Finally, U.S. Pat. No. 1,938,716 suggests extruding certain metal additives which are soft enough to be extruded into the bottom of a vessel or ladle. It is further taught in the '716 patent that with the extrusion of sodium metal into the molten metal bath. The sodium must be kept below the melting point thereof (100.degree. C.) Because sodium will not react with ingredients of a steelmaking bath at steel making temperatures, sodium will not function as a deoxidizer as suggested. The introduction of sodium can only serve to chill the melt.
It is an advantage according to this invention to provide a method of introducing addition agents to a molten bath which agents are not necessarily soft enough to extrude by mixing the addition agent with an extrudable metal in sufficient quantity such that the mixture can be extruded into the vessel or ladle. It is yet another advantage to extrude an addition agent into the lower portion of the vessel containing a metal comprising first mixing with a nonalloying (with the melt) and vaporizable (at the temperatures of the melt) metal carrier which mixture may be extruded.